Another significant aspect is the linkage between access to information via Web and echo chambers. As a matter of fact, social media tend to suggest the following and interacting with profiles and pages that share similar contents, have similar views and agree with the users. Users select information adhering to their system of beliefs and tend to ignore dissenting information, forming the so-called echo chambers, polarised groups of like-minded people who keep framing and reinforcing a shared narrative. For example, Facebook is often claimed to accelerate the emergence of echo chambers, in which pro- and anti-vaccination attitudes are constantly reinforced, bringing a worrying polarisation of the users [1]} [2]}. The existence of echo chambers may explain why social-media campaigns, that provide accurate information, have limited reach and be effective only in sub-groups, even fomenting further opinion polarisation. Furthermore, when polarisation is high, misinformation might easily proliferate [1]} [2]}.
